Storing Bulk Sugars?

I just bought 50 # of ps and granulated sugars at Sams - I usually store these in sterlite containers I bought a few years ago @ wal-mart. It recently occurred to me that although I ONLY keep sugars in these containers, they still may not be "food safe". I think they're 54 qt, but can't be sure (no label). I'm just wondering what those of you who purchase in bulk store your sugars in, if they're "food grade" or whatever, and what size do I need to hold a 50 # of sugar?

I don't buy bulk just because I don't have a food-safe container to store it in....they are expensive!

I know GFS (Gordon Food Service) sells them (Cambro and Rubbermaid are some brands).

Are you pouring your sugar out into the container or just putting the opened bag in there to keep critters out? I would think it would be okay to keep the bag in there, if the sugar isn't coming in direct contact with the plastic, which probably isn't food-safe.

I just keep it in the original bag and put the bag in a bin I had made.

The bin is really cool. It looks sort of like a window seat (but not in front of a window, so a bench) but the top flips up and the inside holds 2 50# bags + 2 20# bags. When closed you can sit on it in my kitchen.